The present invention relates generally to satellites, and more particularly, to improved passive intermodulation free multilayer thermal blankets for use on satellites.
Typical hardware components employed on satellites must be made xe2x80x9cpassive intermodulation (PIM) freexe2x80x9d by adjusting component design and careful inspection of workmanship. Items that have been known to cause passive intermodulation, such as intermittent metal contacts, corrosion, metal or metal-graphite joints, and untightened or loose connections, for example, must be eliminated from the hardware components by design or careful quality inspection of the hardware and PIM testing at the satellite level. However, typical conventional thermal blankets generate significant passive intermodulation products.
It is an objective of the present invention to provide for improved passive intermodulation free multilayer thermal blankets for use on satellites.
The present invention provides for an improved passive intermodulation free multilayer thermal blankets and assemblies thereof. The passive intermodulation free multilayer thermal blankets and assemblies may be advantageously used as components on satellites and other spaceborne vehicles.
A first exemplary passive intermodulation free thermal blanket Comprises multiple layers of reinforced, carbon-loaded polyimide sheets followed by thin polyimide or polyester sheets with metallized film (aluminum) applied on one side only. The metallized sides of the polyimide or polyester sheets are oriented in a single direction so that no metallized film layers touch each other. The metallized film layers are bound together with a combination of polyimide tape, aluminum foil tape with conductive adhesive, and carbon loaded polyimide film. The carbon containing polyimide sheets are placed over the metallized sheets and wrapped around the metallized layup to form a hem on the back side of the blanket. Films are perforated with the exception of the outermost metallized layer to allow for venting of the thermal blanket.
A second exemplary passive intermodulation free thermal blanket comprises multiple layers of reinforced, carbon-loaded polyimide sheets covering thin polyimide or polyester sheets with metallized film (aluminum) applied on one side only. The metallized sides of the polyimide or polyester sheets are oriented in a single direction so that no metallized film layers touch each other. The thin metallized film sheets are sized in relatively small patches whose edges are individually bound with a combination of polyimide tape, aluminum foil tape with conductive adhesive, and a carbon-loaded polyimide film. The metallized patches each have a carbon-loaded polyimide grounding insert and are assembled together to form a quilt of patches, with each patch electrically grounded to the next adjacent patch through the grounding insert. Carbon-loaded polyimide films (outer covers) cover the entire patch-quilt assembly. The carbon containing polyimide outer covers are placed over the metallized sheets and wrap around the metallized quilt to form a hem on the back side of the blankets. Films are perforated with the exception of the outermost metallized layer to allow for venting of the thermal blanket.
The present thermal blankets do not generate passive intermodulation in and shield underlying passive intermodulation generating hardware from environments containing high intensity UHF (300 MHz) through Ka (30 GHz) RF fields at low orders of passive intermodulation. The thermal blankets shield underlying passive intermodulation generating hardware from environment thereby preventing passive intermodulation generation.
The thermal blankets also provide thermal insulation equivalent or better than standard conventional thermal blankets. In addition, the thermal blankets are resistant from UHF passive intermodulation generation after damage from on-orbit mechanical degradation from impacts with micrometeoroids or orbital debris or damage from thermal cycling or radiation.
The design of the thermal blanket allows for internal venting without risk of passive intermodulation generation. The thermal blankets have increased durability, has low mass, and is tailorable to shield against different RF frequencies and intensities.
The size and configuration of thermal blanket components reduces the risk of generating increased passive intermodulation products from damage caused by in orbit degradation, through orbital debris impact, and damage caused by radiation and thermal cycling. The configuration of the thermal blankets allow quick, easy, and low cost manufacturing of blankets and reduced number of electrostatic discharge grounding tads from the blankets.
The thermal blankets allow the use of hardware that normally would generate passive intermodulation products without costly, intensive, and time consuming inspection and testing. Because the thermal blankets shield the underlying hardware from the RF environment, subsystem and individual passive intermodulation testing of flight hardware may not be necessary